The effect of ultraviolet fluorescence on diamond appearance has been hotly debated for at least the past decade. Opinions of even the most experienced tradespeople vary widely. With great conviction, some say that blue fluorescence of different strengths typically enhances a diamond's overall appearance. Others, as convincingly, say that it has a negative effect. To address this controversy, researchers at the GIA Gem Trade Laboratory conducted an experiment on the effects of long-wave ultraviolet radiation on the color appearance and transparency of gem diamonds. Their results are reported in this issue.

This study challenges the perception held by many in the trade that UV fluorescence generally has a negative effect on the overall appearance of a diamond. In fact, the results support the age-old belief that strong or even very strong blue fluorescence can improve appearance rather than detract from it, especially in diamonds with faint yellow body color. This result is consistent with the slightly higher 'asking' prices reported for these stones. While the apparent benefits of blue fluorescence are less obvious in colorless to very near-colorless diamonds, they still were evident in the study. This should bring into question the trade's lower 'bid' prices for moderate to highly fluorescent diamonds in the better colors. It also makes us question the source of the present controversy surrounding fluorescent diamonds. It may be the result of trademembers' misunderstanding of the complexity of the issue, or the extreme price sensitivity in the highest color grades (where there are fewer stones and distinctions are more subtle). Or it may be the fact that it is simply easier to move goods without the encumbrance of a reported fluorescence.

To some extent, this type of research project is unusual in gemology, in that human observation rather than instrumental analysis is the key tool. Yet evaluation of this human element is just the kind of important research that is needed to help resolve misunderstandings and false perceptions among members of the trade and even the consuming public. Gemological research involves not only the physical, optical, and chemical nature of gems, but also the visual assessment of stones in buying and selling situations. GIA will never alter its course of promoting the scientific examination of gem materials to seek knowledge and understanding, but we also want to encourage more research studies that address important trade concerns.

Thus, we believe that the diamond fluorescence article is as significant a contribution to gemology as the synthetic moissanite and synthetic emerald articles also featured in this issue. After all, the science of gemology is not just about R.I.'s and S.G.'s, or even sophisticated chemical and spectral analysis. It is also about dispelling (or, in some cases, confirming) beliefs that have been perpetuated over the years, and about separating bias and tradition from reality in the gem industry.

Click here to download "A Contribution to Understanding the Effect of Blue Fluorescence on the Appearance of Diamonds"  (PDF file)